As is well known in the art, an electronically operated fuel injection system for an internal combustion engine is adapted to inject fuel into each of the power cylinders of the engine at a rate controlled through detection of various operational parameters of the engine so as to produce in each power cylinder a combustible mixture having a properly controlled air-to-fuel ratio. Such a fuel injection system consists essentially of a solenoid-operated fuel injection valve, sensors to detect such operational parameters and a control circuit adapted to produce signal pulses having pulsewidths varied in accordance with the detected operational parameters of the engine.
One of the operational parameters thus detected in an electronically operated fuel injection system is the rate at which air is to be inducted into each of the power cylinders of the engine. In a prior-art electronically operated fuel injection system, the air induction rate is calculated on the basis of the output speed of the engine and the degree of opening of the throttle valve provided in the air induction unit of the engine. If the engine using such a fuel injection system is of the type equipped with a supercharger to "blow" air into the power cylinders, the air induction rate thus calculated is not in conformity to the actual air induction rate. This makes it impossible to properly control the air-to-fuel ratio of the mixture to be combusted in each of the power cylinders. The present invention contemplates provision of an improved fuel injection system eliminating such a problem encountered in a conventional electronically operated fuel injection system.